LGB-6 to LGB-23 Series 2 – Control Supplement
II Gas piping
1.Size gas piping considering —
a.Diameter and length of gas supply piping.
b.Number of fittings.
c.Maximum gas consumption (including any possible future expansion).
d.Allowable pressure drop from gas meter outlet to boiler. For pressure drops, see
2.Size natural gas piping from Table 3, below. Size piping to provide proper inlet pressure to gas valve when operating at rated input.
a.Inlet gas pressure to manual main
minimum 7" W.C. standard (5" on special order) – maximum 13" W.C.
b.If pressure to gas valve exceeds 13" W.C., install positive
c.To obtain approximate cubic feet per hour, divide input (BTU/HR) by 1000.
3.Remove gas supply knockout disc from jacket panel.
4.Follow good piping practices.
5.Pipe joint compound (pipe dope) must be resistant to corrosive action of liquefied petroleum gases. Apply sparingly only to male threads of pipe joints.
6.Install drip leg at inlet of gas connection to boiler. Where local utility requires, extend drip leg to floor.
7.Install ground joint union when required for servicing.
8.Support piping by hangers, not by boiler or its accessories.
9.Purge all air from supply piping.
10.Before operating boiler, check boiler and its gas connections for leaks.
Do not check for gas leaks with an open flame – BUBBLE TEST. Failure to use bubble test or test for leaks can cause severe personal injury, death or substantial property damage.
a.Close manual main
b.Disconnect boiler and gas controls from gas supply piping during any pressure test greater than 13" W.C.
11.Set gas pressure switch as follows or to local inspector’s requirements
a.High – 14" W.C.
12.Canada only - manual main
Table 3
Natural gas supply pipe sizing
Pipe |
| *Pipe length, in feet (Natural Gas capacities, listed in MBH) |
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Size | 10 | 20 | 30 | 40 | 50 | 75 | 100 | 150 |
1 ¼" | 1,050 | 730 | 590 | 500 | 440 | 360 | 305 | 250 |
1 ½" | 1,600 | 1,100 | 890 | 760 | 670 | 545 | 460 | 380 |
2" | 3,050 | 2,100 | 1,650 | 1,450 | 1,270 | 1,020 | 870 | 710 |
2 ½" | 4,800 | 3,300 | 2,700 | 2,300 | 2,000 | 1,650 | 1,400 | 1,130 |
3" | 8,500 | 5,900 | 4,700 | 4,100 | 3,600 | 2,900 | 2,500 | 2,000 |
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4" | 17,500 | 12,000 | 9,700 | 8,300 | 7,400 | 6,000 | 5,100 | 4,100 |
*Include measured length of gas supply piping and allowance in feet for number and size of fittings.
4 | Part Number |